Automatic drill



G. w. SMITH AUTOMATIC DRILL July 8, 1958 Filed May 27, 1957 INVENTOR GEORGE W. SMITH BY Ll/afifw i ATTORNEY United States AUTOMATIC DRILL George W. Smith, Augusta, Ga. Application May 27, 1957, Serial No. 661,922

3 Claims. (Cl. 128310) This invention refers generally to medical devices and, more particularly, to instruments utilized by medical practitioners in the operations performed to the skull or bone structure of a human being or animal.

This application is a refile of U. S. Patent application Serial No. 184,738, filed by applicant on September 14, 1950, for Surgical Bone Perforator with Safety Stop, now abandoned.

Surgical operations are practiced on the human skull bone for many conditions, which are detrimental to the well being and health of the individual and require drastic surgery to ameliorate the condition. To perform such operations, it is customary to drill holes through the skull bone with a hand brace of a design very similar to that used by carpentering mechanics to saw through the bony structure.

The objections to the use of such instruments arise from the fact that such tools will cut through the skull and damage the meninges or brain and do not leave the parts in a condition that enables them to heal to a condition approximately equal to that which existed originally.

Thus, when holes are drilled in the bone structure, the material removed is mostly in powder form, and not reusable. This leaves a space in the structure of the bone which nature does not provide means to fill up and quickly heal elfectively.

While the instrument included in this invention is intended primarily for craniotomy, it is quite practical and feasible for it to be used also for drilling holes in any of the bones of the human or animal body.

It is an object of this invention to provide a new and improved combined perforator and burr unit for surgical work which will avoid some of the disadvantages an limitations of the prior art. 7

Another object of the invention is to provide a new and improved osseous tissue drilling unit which will drill the tissue in such a manner as to enable the residue thereof to be reused in the opening made to facilitate healing.

A further object of this invention is to provide a new and improved osseous tissue drilling unit which will automatically control its own operation to suit the structure of the tissue being operated on by it.

An additional object of the invention is to provide a new and improved osseous tissue drilling unit which will have its components designed to permit them to be quickly and conveniently dismantled for cleaning, sterilizing, and replacing.

Still another object of the invention is to provide a 1 new and improved single drilling unit for perforating bone structure which will automatically stop drilling by allowing the driving force to be disengaged as soon as the last shelf of the inner table is removed at the base of the opening.

And still another object of the invention is to provide a new and improved drilling unit for surgical purposes which will be convenient and effective in use, and which injury to the meninges or the brain.

v 2,842,131 Patented July 8, 1958 will greatly facilitate the functions of the operations done in the classes for which it is intended.

To provide a combined perforator and burr unit which is economical to manufacture, efiicient and reliable in operation, and easy to assemble and maintain, are other objects of this invention.

These and other objects and advantages of this invention will become more apparent from the following detailed description and accompanying drawings in which:

Fig. 1 is a side elevation of a combined perforator and burr unit embodying this invention shown in position for cutting through the skull:

Fig. 2 is a view similar to that shown in Fig. 1 after the perforator and burr unit has cut through the skull;

Fig. 3 is a sectional view taken on line 33 of Fig. 2; Fig. 4 is a top plan view of the invention;

Fig. 5 is a bottom plan view of the invention;

Fig. 6 is a sectional view taken on line 66 of Fig. 3;

Fig. 7 is a sectional View taken on line 7-7 of Fig. 3;

Fig. 8 is a sectional view taken on line 8-8 of Fig. 3;

Fig. 9 is a side elevation of the wrench used for assembling the unit.

In accordance with the invention, there is provided a combined drill and counterbore unit which makes a sheer, complete trephine opening in the bone structure, thus requiring only one instrument. It will automatically stop drilling by allowing the driving force to be disengaged once the last shelf of the inner table is removed at the base of the opening.

This instrument, which can be driven either manually or by motor, makes a trephine opening safely with no The unit or bit accomplishes this by providing multiple cutters slidable over one another with a resiliently operated clutch serving as means for enabling them to operate together and independently.

The cutters are arranged to remove the bone structure in large generous bone chips so that it can be replaced and reincorporated in the hole structure after the operation is performed. Further, when the unit perforates the Wall of the bone structure and projects therefrom, it automatically stops so no further cutting willbe done. The opening is clean of bone chips, and has sheer shoulders and is completely through the skull.

The components of the instruments are made so they can be fitted together accurately and operate without excess movement. The arrangements for tightening or fastening the parts can be performed with the least amount of tools principally by, designing the components so they can function as a part of the device in one position and as a tool for securing the parts of the unit together in another.

The use of the term drilling as employed in this application is intended to be broad enough to include any usual drilling, milling and cutting work performed by a rotative tool. Similarreference numerals refer to the same parts throughout the drawing.

The particular form of the instrument shown is that especially adaptable for craniotorny operations, but may be used for other osseous operational work. The instrument consists of a combined drill and counterbore unit having several components, including a primary drill 10, which is slidable and guidable freely in ashank or spindle proper 59 is arranged for insertion in 6 a conventional chuck rotated by a suitable drilling machine, not shown.

A tapered coil spring 60 has its larger end placed within the thimble 3t) and against the shank member 50 at its smaller end. it serves as a resilient propellant to disengage the drill 1t and the safety counterbore collar 20 from the driving mechanism after penetrating the skull.

The primary drill 16 is preferably made of solid material of suitable strength and capacity with four spaced cutter blades 11 formed thereon as indicated in the drawings. These blades 11 extend from the cylindrical body 12 of the drill 10. The cutting faces 13 of the blades 11 are preferably sharpened to approximately 18 positive pitch into the form shown for removing a semi-continuous shaving from the bone or osseous tissue when the drilling is done in the skull or other osseous structure of the human or animal body.

Th cylindrical body 12 of the drill is internally threaded at 14 with a raised or extended shelf 15 of lesser diameter than that of the base diameter.

A slot 16 is cut in the peripheral wall of the base, and is of suitable depth and contour to receive and hold a drive key 18 fastened in place, flush by a countersunk screw 17. The key 18 is formed as illustrated and has a projecting end portion 19 of apexed contour resting against the peripheral wall of the shelf 15. This key 18 serves as a tooth to be engaged in a slot 26 in the flange 49 of the counterbore collar 24) so that they will normally both mesh and rotate together.

Both the drill 10 and the counterbore 29 are adapted to cut into the bone structure being operated on, but the blades 21 on the latter are approximately 9 shorter and do not act until the blades 11 have progressed to a predetermined depth. The blades 21 Will continue as a counterbore until the inner face of the bone is passed through by the blades 11. Then the drill 10, being unobstructed, slides forward and disengages the key 18 from the drive cylinder 40.

The cutting faces 23 of the blades 21 have approximately an 18 pitch and are designed to cut as a counterbore about the hole or opening made by the blades of the drill 10 and, when the latter stops rotation due to the disengagement mentioned to rest on the shelf cut by the counterbore, it thereby prevents further entry of the drill through the skull.

The drill it} cannot slide more than 4;" or so because of the limitations imposed by the allowable movement permitted by the assembled relationship of the drill 10,

counterbore collar 20, thimble 30 and drive cylinder 40 with one another. The collar has its blades 21 spaced around it to align over and with the blades 11 of the drill 10. its flange 49 is slotted at 26 as noted previously. The slot 26 in the flange 49 of the collar 20 is of a width sufiicient to allow the key 18 to easily engage therein when these particular parts are driven together.

The thimble 39 is preferably of the form shown in the drawings. duced in diameter between a base flange 31 and a top flange 33 in order to reduce friction and permit free axial movement within the driving cylinder 40. The flanges 31 and 33 are finished off to fit in the interior of the cylinder 40 accurately. so as to be guided longitudinally therein.

A base 32 of lesser diameter extends from the base flange portion of the thimble for a predetermined amount and is then surmounted by a threaded stud 34 forming a shoulder 35. The stud 34 screws into the threaded hole 24 of the drill 10 until the shoulder 35 butts up against the upper face of the drill 10 and joins them tightly to one another.

A slot 36 is provided in the wall of the thimble 30 for enabling it to be held by a spanner wrench in a manner to be described later. The thimble 30 is drilled to provide a bore 37 to receive the larger end of the coil spring 60.

It is generally cylindrical in shape and is re- The drive cylinder 40 has an inside diameter large enough to receive the flanges 31 and 33 of the thimble 30. When fully inserted therein, the thimble 30 has its base flange 31 in close contact with a lug 41 which extends inwardly at the end normally placed against the drill 10 and counterbore sleeve 20. This lug 41 keeps the thimble 30 in place in the cylinder 40. It also acts as a driver to transmit rotation to the cutting collar 20 and drill 10 through the key 13. The cylinder 40 is threaded internally at its upper end and its wall is provided with a hole 56 to take a spanner wrench when inserted to en gage slot 36 in wall of thimble 30 to prevent its turning when the drill 10 is attached.

The shank member is formed with a knurled collar :31 and a reduced portion 52 which is provided with male threads to fit into the threaded upper end of the cylinder 48 and bring the collar 51 flush against the upper end of cylinder 40. A stem 53 projects axially from the bottom of the shank 50 and has its free end portion of tapered form, like that of a screw driver blade.

This stem fits into and holds the coil spring 60 in place in the bore 37 in thimble 36 so that it can exert pressure from the member 50 onto and against the thimble 30. A cross piece 55 extends across the shank member 50 above the knurled collar 51 and has flat faces 56 planed oti suitably to enable the chuck to hold the member 50 rigidly while its spindle 59 is held therein in a conventional manner.

The operation of the instrument will make the structure of the invention easier to appreciate. The components are normally positioned as indicated in Figs. 2 and 3. it is assumed that the instrument is attached to a drilling machine chuck in a conventional manner, and is rotating on its longitudinal axis. The drill 10 is brought against the bone to be drilled preferably in a position at right angles to its surface. When pressure is exerted on the instrument, the shank member 54) with its cylinder 40 is pressed downward and is moved close against the counterbore collar 20 and drill 10. In this position, the key 18, which is meshed in the slot 26 in the collar 20, then engages the lug 41 in the drive cylinder 40 and then are rotated together by shank member 50. The hole 46 in cylinder 40 permits insertion of an end tooth 61 of spanner wrench 62 into the slot 36 in thimble 30, thereby enabling the thimble 30 to be held against rotation so that drill 10 may be secured onto or be removed from stud 34. The stem 53, while intended primarily as an anchor and for keeping the spring from buckling, also serves as a screw driver for installing or removing the screw 17 holding the guide key 18 to drill 10.

This guide key 18 is also intended to be employed as a shear pin in case the instrument is stopped or caught while the operation is going on. When the drill 10 passes through the bone 64 proper and before it reaches the meninges 65 covering the brain, it has nothing to press against and cut, so it slides down under pressure of spring 60 and in doing so disengagcs the key from the lug 41 in the cylinder 40 so that the drill 10 and counterbore collar 20 will stop rotating even though the spindle 59 is being rotated by the drilling machine. The perforating operation will then stop. In Figs. 1 and 2 of the drawings, the thickness of the meninges 65 and the space separating them from the underside of the skull bone 64 are somewhat exaggerated to emphasize the free movement of the drill after it has perforated the bone'64.

The instrument is particularly valuable for the work in question as it operates automatically in its starting and stopping function and prevents the operation from being performed beyond the desirable point of depth. The parts are readily assembled and disassembled so that they can be easily and conveniently sterilized, or the cutting components repaired or replaced. There are no projecting parts that might catch on the clothes or the hands of the surgeon or nurse. It can be made up in compact form and designed to fit the general requirements desirable in surgical instruments without involving complicated construction or special handling or tools. It cuts holes with its blades so a semi-continuous shaving will be derived from the bone during the operation. After the operation, the shaving in its helical strips is returned carefully into the hole and allowed to incorporate with the walls about the hole and expedite its filling and healmg.

While but one general form of the invention is shown in the drawings and described in the specifications, it is not desired to limit this application for patent to this particular form, as it is appreciated that other forms of construction could be made that would use the same principles and come within the scope of the appended claims.

What is claimed is:

1. A drilling implement for bone structures, comprising, a drill, a counterbore collar surrounding said drill, said drill and collar being relatively longitudinally slidable, a drive cylinder aligned with said drill and collar, a closure head at the upper end of said cylinder, clutch means between said drive cylinder and drill, said clutch means also maintaining said drill and collar for conjoined rotary movement, whereby said drill and collar rotate when said drive cylinder rotates, and means between said closure head and drill for disconnecting said clutch means between said drill and said drive cylinder and forcing said drill axially ahead of said collar when resistance to the cutting action of said drill ceases.

2. An arrangement as set forth in claim 1, wherein said clutch means consists of a key secured to said drill,

said drive cylinder having a shelf in proximity to the upper end of said drill, said collar having an internal ledge at its upper end, said key extending upwardly through said internal ledge and abutting said shelf of said drive cylinder.

3. A drilling implement for bone structures, comprising, a drill, a counterbore collar surrounding said drill, the cutting edges of said drill being arranged to extend beyond the cutting edges of said collar, said collar and drill being relatively axially slidable, a drive cylinder co-axial with said drill and collar, a'closure head at the upper end of said cylinder, clutch means between said drill and said drive cylinder, said clutch means also maintaining said drill and said collar for conjoined rotary movement, whereby said drill and collar rotate in unison when said drive cylinder rotates, a thimble mounted within said drive cylinder, connecting means between said thimble and said drill, and a spring forcing said drill against said bone structure, said spring having'one end abutting said thimble and its other end abutting said closure head, said spring disconnecting said clutch means between said drive cylinder and drill and causing axial movement of said drill within said collar when said drill protrudes through said bone structure and the resistance to said spring is thus removed.

References Cited in the file of this patent UNITED STATES PATENTS 12,728 Martel June 6, 1910 2,131,845 Nutt Oct. 4, 1938 2,504,075 Karle Apr. 11, 1950 2,525,669 Hainault Oct. 10, 1950 

